1. Industrial Application
This disclosure is for a lift table equipped with a table which, through a scissor-link mechanism, maintains itself level with the base.
2. Description of Related Art
Previous lift-table designs include the apparatus described in Japanese Application 4-13465 (1993), which consists of a portable lift table with a spring set below the base whose upper end is attached to a series of pin holes paralleling the upper spring holder attached to one link, thus allowing for a change in the position of the spring and for adjustment of the height of the table according to the weight of the products being used on the work platform.
Another model is disclosed in Japanese Application 56-171375 (1981) having a main link attached to the portable base, a sliding horizontal shaft along the main link, and an auxiliary link with a spring between the aforementioned horizontal shaft and the area below the base of the lift table; the table is supported by the spring, and an adjustment mechanism allows the lower end of the auxiliary link to change position and allows for adjustment of the effective spring rate.
The first model mentioned above, due to its structure which allows for only discrete changes in position because of the pin holes in the upper spring holder, makes it impossible to make small adjustments in the effect of the spring rate and maintain a set height for the table to match each product and weight being used.
Moreover, because the spring is held in place by pins and pin holes, when the position is changed by pulling a pin out, the spring loses its effectiveness and there is a serious danger that the table will collapse. The 1981 model mentioned above has its adjustment mechanism set under the portable base; so, it is difficult to use. It is also difficult to ascertain the adjustment position and, since the mechanism is such that the spring does not directly act on the scissor links, stress acts on the auxiliary link and the horizontal shaft which keeps the spring in place, making the table lose its support capability.
Furthermore, since both of these models have the spring and spring holder projecting below the base, it is necessary to have casters and legs, and the base set above ground level. In addition to increasing production costs, when the ground is uneven the aforementioned projecting components may strike the ground while the entire platform is moved, and there is a possibility of damage to the platform.